jwaas.es@PARC-MAXC.ARPA (03/08/84)
This is in response to a question regarding repairs to the IBM logic and the video display. The flyback is a quite common transformer which most T.V. parts supplier will be willing to sell. The cost would be around $20 . The type might be decernable from the actual unit but most often a good parts man can find one of several replacement types. When installing, first wash your hands very well to remove oils and salts which can cause arcing problems on the transformer body, then, if soldering any wires, when soldering create smooth well rounded balls without peaks if soldering any wires. The printed circuit board soldering needs only normal soldering methods. The cost of replacing the entire board could be avoided if taken to a good technician. I found a tech. who works on 8085,8086 and Z80 machines. He charges $100 minimum which covers the first hour of his work. Parts are extra. But he repaired my Z80 machine for $165 which beat the $480 replacement cost although it did take him 3 days. Jaye
pwl@fluke.UUCP (Paul Lutt) (03/19/84)
It has been suggested in this group that the IBM monitor could be
repaired by any competent TV service type. While this is possibly true,
it should be noted that the IBM monochrome monitor runs at 18 kilohertz,
not the more usual 15,750 used in all normal NTSC compatible televisions.
Replacing the IBM monitor's flyback transformer with one from a normal TV
would most likely burn out the horizontal drive system. This is because
flyback systems in CRT systems are highly tuned. Using a component designed
for a different operating frequency from the one originally installed will
unbalance this tuning, causing excessive power consumption and overstressing
of drive components.
The modern CRT is a marvel of design, but it must be kept in mind that
just because the tube sitting on your computer LOOKS like a normal television
doesn't mean that it is necessary the same. Find out what you have before
you attempt to repair it.
Paul Lutt
John Fluke Mfg. Co., Inc.
Everett, WA
{uw-beaver,decvax!microsof,ucbvax!lbl-csam,allegra,ssc-vax}!fluke!pwl